1. Field
Embodiments described herein relate to a non-volatile semiconductor memory device.
2. Description of the Related Art
In recent years, resistance change memory (ReRAM) in which a variable resistor is employed in a memory cell have been proposed. An operation of writing data in a memory cell is performed by applying a certain set voltage to a variable resistor. This causes the variable resistor to transition from a high resistance state to a low resistance state. Hereinafter, an operation to change the variable resistor from the high resistance state to the low resistance state is referred to as a “set operation”. An operation of erasing data from a memory cell MC is performed by applying a reset voltage to the variable resistor, which remains in the low resistance state after the set operation, in an opposite direction to a direction in the set operation. This causes the variable resistor to transition from the low resistance state to the high resistance state. Hereinafter, an operation to change the variable resistor from the low resistance state to the high resistance state is referred to as a “reset operation”.
In resistance change memory, when the resistance values of the variable resistors disperse during the set operation or the reset operation, it is difficult to store accurate data in memory cells. For this reason, in resistance change memory, it is necessary to suppress the dispersion of the resistance values of the variable resistors during the set operation and the reset operation.